30/07/2013

On the theme of youtube videos - here a little seen gem - Former F3B world champ Nic Wright giving an F3B demonstration to Australian fliers. Note how he reels off some super fast speed runs with consummate ease.

If, like me, you spend a lot of time pondering how to best throw an f3b model, here's a video you might enjoy. Or if you just like cool stuff in slow motion. Previously posted on the Barcs Forum, but worth another airing.

23/07/2013

F3B Using Electric Motor Launch

Entry numbers in flat field soaring classes have been in decline in recent years in the UK and elsewhere. Most people feel that electric flight is the future of many aspects of flat field soaring. The benefits are many - space requirements, simplicity, ease of use etc. The concept of F3B electric is simply to replace the traditional winch launch with an electric launch to a height determined by a limiting device - several such devices are available for e-soaring and F5J. Otherwise the rules remain the same with each competitor flying duration, distance and speed tasks. Using height limiters means it is possible to fly electric F3B models against winch launched models, in a mixed competition.

The technology of brushless motors and particularly lipo batteries has improved enormously in the last few years. This has also coincided with significant advancements in composite technology for rc gliders. At the time of writing it is possible to buy a 4m glider that weighs under 1.8kg at flying weight. With the increasing popularity of F5J there are now a number of airframes for electric flight that are even lighter than their "pure" glider F3J equivalents because they don't need to be built to withstand a two man two or winch launch.

The situation is somewhat different in F3B, where the power requirements are considerably greater than F3J and F5J. Clearly an electric version of an F3B model requires a power-set that can launch the model with ballast for the speed and distance tasks. F3B launch heights are typically well over 250m, so an equivalent electric set up needs to be able to launch a ballasted model (say 3.5kg) to height in a reasonable time. The model will still also require a strong wing due to the g-forces encountered in speed. F3B models are also designed for minimum drag and therefore have very thin fuselages.

An F3B-electric power-train set up needs to 1) Provide a large amount of power 2) Fit in a small space 3) Not increase the weight of the glider to the detriment of its duration soaring abilities

To that end electric F3B pioneer, Clive Needham, has been working with Tony Fu of Sloperacer to find a suitable motor combo for for F3B electric. Clearly inrunner motors have a smaller diameter than outrunner motors, but offerings from the likes of Kontronic and Hacker typically state max power outputs of around 500 watts, which is inadequate. The motor/gearbox combination that Tony has devised is a special long Leopard inrunner coupled to a Reisenauer gearbox. Diameter is 28mm, max power is over 1kw, with high efficiency. Clive has done a considerable amount of flying with his electrified Dingo and has found that the model performs very well.

With the availability of 70C batteries, at the time of writing, and no doubt more in the future, the setups we have been experimenting with are not adding significant weight to the airframes. Nor are they spoiling the look of these graceful models.

I think it is possible that F3B airframes can be made lighter for electric launch, with fuselages specifically design for motor installation. Whether this will happen depends on the future F3B situation in the central European countries, such as Germany and the Czech Republic, which are the core areas of F3B competition and model design. If people in those countries take an interest in F3B electric, clearly specific models will start to appear, with pre-installed motor mounts and better battery access. At the time of writing very few if any of the top F3B models are available with a electro fuselages, and if they are it is a large fuselage for a hotliner set up. However, some F3B models can already be flown at 1.9kg which would probably only be about 2.1-2.2kg with an electric motor. At this stage we are mostly modifying existing fuselages to take the electric power trains. Samba Model, of Pike fame, has recently released an electro fuselage for its Pike Precision F3F/F3B model, which looks promising.

Advancements in battery and motor technology will no doubt continue apace, which will result in lighter more powerful setups. Currently we are looking at power outputs of around 1.2kw with a 4 cell lipo with the Sloperacer motor (the logging facilities of Castle Creations ESCs have been useful). These models also make great sport fliers as well, of course.

Hello! I am reviving the f3b UK blog. Thanks to Chris Jubb.

The first post is a report from League 4, 2013. With the recent "heat wave" (aka summer) that we have been experiencing it was possibly a relief that the weather for Sunday was overcast and fairly mild (with even a few rains spots at times). Personally I didn't fancy lugging the gear around in 30 degree heat all day.

However, the overcast conditions and the fairly bright light made for a sky that was difficult to pick out models in, and was a challenge all day when flying at duration distance. What was generally reckoned to be a wave was fairly consistent from the east at a considerable distance beyond the winch line. With the general lack of obvious thermals, the best tactic for duration was to push out in front and carefully ride the wave in combination with the slight slope lift from the right of the field. In spite of the difficulty in seeing models, there were few low scores in duration with most people achieving good times. A good launch was very helpful, giving you the chance to range out to find the lift.

Conditions for launching were quite decent, with a moderate wind. If you could steer your model off to the left and swing back in to the wind a decent launch was definitely possible. Not too much score separation happened in Round 1 of duration. A few people dropped a minute or two or messed up the landing, but there were no real clangers. Mike Holtby's Cobra again showed it's ability to pull big tension on the line and float very well when required.

Distance conditions were reasonable but not epic, with the lift again being most consistent to the right of the course, with most people choosing to fly that direction. I think Bob had a go on the other side and did okay. In fact Bob was unlucky as he had a huge launch it to great air on his first distance round, but the round was cancelled when a parachute being wound down in a cross wind knocked down base B (sorry Bob)!

Clive put in a good stint scoring a very respectable 23 legs in round 1, which was the best score of the competition. Young Simon put in a good performance scoring 21 legs in both rounds and only dropping 45 odd points. Clive, Steve Haley, Mike Challinor and John Whittle scored the maximum 1000 points in both rounds. Distance scores were fairly close without most people dropping or gaining too much over the field.

On to speed where times were generally in the high teens for a good run, with the exception, again, of Steve Haley who took a couple of seconds out of the best of the rest following a good launch and consistent flying (15.xx seconds). This took nearly 130 points out of his nearest rival which would prove critical in the final scoring. Bill wasn't quite back to his usual self, but it was good to see him flying again. Round 2 of speed followed a similar pattern to the first round with times of about 17 seconds being competitive. I put in a new personal best of 17.31, which to my surprise, took the 1000 points for the first time, beating Mike and Steve by few tenths. Happy days! Brian dropped quite a few points in speed, which I am sure he will be looking to improve with his Ascot, which seemed to be showing good potential - it's a well proven model of course.

Round 2 of duration followed a similar pattern to the first with mostly high scores. Unfortunately Clive was not able to fly the round due to technical problems with his electric model, which was a shame as he had scored well to that point. I enjoyed a fun round against Steve were we both gently rode the wave, indicating lift and sink for each other and swapping heights and position throughout the slot. Eventually I came out just on top with a 10.00 / 100 point flight that was a nice way to end the comp for me.

So all in all another very enjoyable round. I don't think there were damaged models. Perhaps Clive's prop blades took a bit of a beating when he tried to repay the farmers kindness in helping get Steve's esoaring model out of the tree, by strimming the grass for him. Kudos to Steve, as it takes a top drawer flyer to truly park a model in a totally inaccessible place. The model only being retrieved thanks to Bob's slightly disturbing expertise with a chainsaw. Whether he just carries it round in the back of his car in case of emergency, I don't know.

Special mention must go to Phil Goddard who flew most, or all, of the competition with his transmitter set to the model memory of one or more different models, which may or may not have had something to do with f3b or even gliders. The word on the flight line seemed to be "Wot4," which we can only assume is a model that doesn't have the same trim settings as a ceres lift. The winner was Steve Haley, with his round 1 speed score proving to be decisive over 2nd placed Mike C. Simon Haley came in third having flown consistently all day. He narrowly pipped John Whittle, who lost a few crucial points in the final duration slot. I was fifth, follwed by Bob and Mike Holtby. Dave Worrall and Brian Johnson scored good points and will be looking to the nationals no doubt. Clive and Phil suffered non serious "technical" problems and Bill was still feeling his way back after recent ill health.